If you are working with pixels just muliply the length by 3 and make sure that the length and width are linked so they change together. If you can set it to inches and you know how big the poster is that would be prime.
This will come up with options like X and Y in pixels or inches. Under edit there should be a 'Canvas size' or 'Image Size'. Next you need to make your canvas large enough to hold all of the parts. Start with the upper left corner for example. I would use a digital camera to capture the poster but I will help with your question a bit anyway.īe systematic.
